The present invention relates to an antenna for a radar system. More specifically, the present invention relates to an antenna for an aircraft weather radar system that scans a first direction by rotating about one axis and scans a second direction by electronically steering the radio frequency (RF) beam.
It is generally known to provide for an antenna for an aircraft weather radar. Such known antennas typically include a mounting apparatus and an antenna coupled to the mounting apparatus by an elongated structure. Typical radar scanning antennas utilize mechanical scanning, relying on motor and gear arrangements to physically rotate and tilt (elevate) the antenna. FIGS. 8 and 9 illustrate an exemplary known aircraft weather radar system 100. Radar system 100 includes an antenna 102 and a mounting apparatus 104. The mounting apparatus 104 includes a base 103 and a support arm 106 extending from the base 103 and configured to support, among other components, the antenna 102, a horizontal drive motor 105, and a vertical drive motor 107. Mechanically scanning both the vertical axis (azimuth) 108 and the horizontal axis (tilt) 109 requires the horizontal drive motor 105 and the vertical drive motor 107 to be mounted close to the pivot axes 108, 109 of the antenna 102 (for mechanical antennas this is close to the center of the flatplate), and requires the mounting apparatus 104 to be in the rotation area of the antenna 102. This generally limits the effective scan angle to 180 degrees or less.
However, such known radar systems have several disadvantages including having limited scan angles, being heavier, occupying more space than desired, and being susceptible to shock and mechanical failure, excess RF power generation to compensate for transmission losses to the moving antenna element through rotary couplings. Also, mechanical scan (azimuth and tilt) antennas have single point failure components, such as motors, bearings, gears, RF switches, and moving interconnects that are susceptible to mechanical breakdown and wear causing undesirable stranding rates. Further, motor sizes to compensate for vibration, acceleration, and deceleration are larger and dissipate more power than desired. In addition to these “mechanized” disadvantages, radome volume and weight reduction is becoming more and more important for aircraft manufacturers in order to increase cargo capacity and passenger comfort. Furthermore, aircraft manufacturers desire better hazard detection capabilities (e.g., turbulence, lightning, windshear, hail, severe weather, etc.) to reduce potentials for aircraft damage and passenger discomfort.
Accordingly, it would be advantageous to provide a radar system that rotates only about one axis. It would also be advantageous to provide a radar system that is lighter, is less susceptible to vibrations, and has fewer components susceptible to failure. It would further be advantageous to provide a radar system with the possibility of an azimuthal scan greater than 180 degrees. It would be desirable to provide for an antenna having one or more of these or other advantageous features. To provide a reliable, and widely adaptable, antenna that avoids the above-referenced and other problems would represent a significant advance in the art.